Recently, magnetic recording media have been widely used as audio tapes, video tapes, and magnetic tapes for computers. In these cases, magnetic recording media are required to have excellent characteristics in electromagnetic conversion characteristics and tape running durability. In particular, excellent electromagnetic characteristics and good running characteristics are very important factors for magnetic recording media and it is necessary to attain the aforesaid two characteristics simultaneously.
For satisfying both the aforesaid required characteristics, a magnetic disc capable of preventing a deviation of output caused by the surface properties of the disc and at the same time improving the durability of the disc by forming pores having an average pore area of from 6.times.10.sup.-5 to 7.times.10.sup.-1 .mu.m.sup.2 (pore diameter of from 86 .ANG. to 9560 .ANG. in the magnetic layer by the random orientation of the magnetic layer has been proposed as disclosed in U.S. Pat. No. 4,759,954.
However, with the demand for high image quality and high tone quality systems such as S-VHS (high quality video) and S-8 mm (compact high quality video) and further with the demand for high quality systems such as High vision (high quality video) and high density type floppy disc, magnetic recording medium for high density recording have been demanded.
For attaining such high density recording, it is necessary to make surface of the magnetic layer super smooth of, for example, less than 5 nm in center line average roughness (Ra). Also, such a super smooth surface of the magnetic layer increases the coefficient of friction thereof, and hence it is further required to improve the running durability of the magnetic tape.
For the aforesaid requirement of high density recording, the above-described average pore area is too large to obtain a sufficient smoothness. Moreover, with a large average pore area the effect of lubricant in the magnetic recording layer does not last due to the large inlet diameter of the pores. That is, since in a conventional magnetic recording medium, the surface of the magnetic layer is not so smooth, the sliding area of the magnetic layer relative to a magnetic head is small and thus there is no serious problem in the sliding characteristics, but since the surface property of the conventional magnetic recording medium is not super smooth, S/N at short wavelength is not improved and hence excellent electromagnetic characteristics are not obtained. Also, since in a conventional magnetic recording medium, the inlet diameters of the pores are relatively large, there is a disadvantage that the lubricant contained in the magnetic layers quickly oozes out and the lubricating effect does not last.
Also, JP-A-62-22239 (the term "JP-A" means an "unexamined published Japanese patent application") discloses that the running stability and the running durability can be improved by incorporating a fatty acid in a magnetic layer of a magnetic recording medium in an amount that the extracting amount of the fatty acid from the surface of the magnetic layer by a nonpolar hydrocarbon solvent is in an amount of from 5 mg/cm.sup.3 to 30 mg/cm.sup.3 per volume. However, in the case of a magnetic recording medium for high density recording having a super smooth surface, a sufficient tape running property and tape running durability are not obtained even when a so-called free fatty acid exists in the magnetic layer as described above.